On an August day 17 years ago, eight Minnesota junior high school students on a field trip caught 22 frogs in a farm pond. At least half of the frogs had some abnormality, mostly in their hind legs. The conscientious teacher reported the group’s finding to the state. Dutiful state scientists surveyed wetlands across Minnesota and found at least one hotspot of frog abnormality in every county in the state.
What have we learned about frog abnormalities in the last 17 years? Quite a bit, actually. There appear to be several causes, and sometimes the causes pile up to create a high rate of abnormalities. The causes also seem to vary by region.
Vermont also experienced a high rate of frog abnormalities back in 1995, but the interpretation there is a bit different than it is in Minnesota.
Are you finding abnormal frogs? A fantastic resource for state biologists evaluating frog abnormalities is the Field Guide to Malformations of Frogs and Toads (with Radiographic Interpretations) by Carol Meteyer of the US Geological Survey’s National Wildlife Health Center.
Photo: Frog with abnormality, by David Hoppe, courtesy of US Geological Survey